Wall Street's main indexes fell on Tuesday after U.S. President Donald Trump's latest plans for pharma tariffs renewed worries of the impact of a trade war, while some downbeat corporate results also weighed on investor sentiment.

Wall Street is poised to open with gains as the U.S. Federal Reserve wraps up a two-day policy meeting where it will almost certainly leave interest rates unchanged despite pleas from U.S. President Donald Trump for a rate cut as he pursues a worldwide trade war.

Stock markets mostly dropped on Tuesday as investors awaited a US Federal Reserve interest-rate decision for signs of the outlook for the tariffs-hit economy.